This invention relates generally to cooling a rotary component, and more specifically, to cooling a wheelspace in a stage of a steam turbine.
At least some known stationary and rotating components found in steam turbine engines are subjected to temperature, pressure, and centrifugal loadings during normal operations. The design of the high-pressure (HP) and/or intermediate-pressure (IP) sections of known steam turbine engines may be complex because of the high temperatures and pressures of the steam supplied to the steam turbine and because of the creep experienced by such components. Known temperatures and pressures that satisfy the aerodynamic and thermodynamic design requirements for at least some known turbines require a corresponding acceptable mechanical design solution. Known design solutions focus on bucket and rotor materials and/or geometries, steam turbine operating temperatures and/or pressures, and/or piping solutions external to the steam flowpath.
To achieve an acceptable mechanical design for some known steam turbine components, some known designs require that such components be exposed to steam temperatures that are at lower temperatures than similar components would typically be exposed to during normal operations of known turbine sections. However, limiting operating temperatures and pressures within the turbine limits the thermodynamic design space and may result in decreased turbine performance.
One known design solution involves changing the rotor geometry and materials to make a rotor that is acceptable for long-term operations, without providing external cooling. However, such geometries are generally more costly, reduce stage efficiency, and/or require costly, higher capability materials than designs that use an adequate cooling scheme. One known cooling scheme uses pipes routed through a steam flowpath to supply a cooling steam flow. For example, such pipes may be positioned within first-reheat, double-flow tub stages. Such pipes however create an obstruction within the main steam flow and add complexity to the system.